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The Trees That Miss The Mammoths

Trees that once depended on animals like the wooly mammoth for survival have managed to adapt and survive in the modern world.By Whit Bronaugh

When it still roamed the earth, the Columbian mammoth acted as a dispersal system for many tree species that still exist today. (Credit: Wolfmansf)

Warning: Reading this article may cause a whiplash-inducing paradigm shift. You will no longer view wild areas the same way. Your concepts of “pristine wilderness” and “the balance of nature” will be forever compromised. You may even start to see ghosts.

Consider the fruit of the Osage-orange, named after the Osage Indians associated with its range. In the fall, Osage-orange trees hang heavy with bright green, bumpy spheres the size of softballs, full of seeds and an unpalatable milky latex. They soon fall to the ground, where they rot, unused, unless a child decides to test their ballistic properties.

Trees that make such fleshy fruits do so to entice animals to eat them, along with the seeds they contain. The seeds pass through the animal and are deposited, with natural fertilizer, away from the shade and roots of the parent tree where they are more likely to germinate. But no native animal eats Osage-orange fruits. So, what are they for? The same question could be asked of the large seed pods of the honeylocust and the Kentucky coffeetree.

To answer these questions and solve the “riddle of the rotting fruit,” we first need to go to Costa Rica. That is where tropical ecologist Dan Janzen of the University of Pennsylvania noticed that the fruits of a mid-sized tree in the pea family called Cassia grandis were generally scorned by the native animals, but gobbled up by introduced horses and cattle. Janzen, who received the Crafoord Prize (ecology’s version of the Nobel) for his work on the co-evolution of plants and animals, had the idea that the seeds of Cassia grandis, and about 40 other large-fruited Costa Rican trees, were adapted to be dispersed by large mammals that are now extinct. He teamed up with Paul Martin, a paleoecologist at the University of Arizona, to develop the concept of ecological anachronisms.

By eating their long seed pods, giant ground sloths were the primary dispersal system for Cassia grandis. (Credit: Dxlinh)

An anachronism is something that is chronologically out of place: a typewriter or floppy disc in a modern office. Leather helmets at the Super Bowl. Or, hopefully, the internal combustion engine in the near future. An ecological anachronism is an adaptation that is chronologically out of place, making its purpose more or less obsolete. A tree with big fruits to attract huge mammals as dispersers of its seeds is anachronistic in a world of relatively small mammals.

In the case of Cassia grandis, Janzen and Martin figured that the foot-long woody seed pods were eaten for their sweet pulp by giant ground sloths and elephant-like gomphotheres. These multi-ton animals had such big gullets that they didn’t need to chew a lot, so most of the seeds passed through the animals unharmed and ready to propagate more Cassia grandis trees. However, the gomphotheres and giant groundsloths disappeared about 13,000 years ago, toward the end of the last Ice Age of the Pleistocene.

Gomphotheres and ground-sloths? The Ice Age? What, you may be wondering, do they have to do with Osage-oranges, honeylocusts, and coffeetrees today?

In terms of evolutionary time, the difference between 13,000 years ago and now is like the difference between Friday, December 31, 1999 and Saturday, January 1, 2000. We may assign those two days to different centuries or millennia, but they are still part of the same week. Likewise, all the animals and plants of 13,000 years ago belong just as much in the present. In fact, they still live in the present, with just one major exception: most of the big and fierce animals are now gone. This happened just a couple thousand years before we invented agriculture and planted the seeds of civilization. Woolly mammoths actually survived on some Arctic islands until after the Egyptian pyramids were built!

The giant ground sloth from London’s Natural History Museum was once a dominant species in North America. (Credit: Ballista)

Today, if you searched all of North America north of Mexico, you would find only 17 species of land mammals that could be called megafauna, a term for animals that exceed 100 pounds. If you exclude the rare predators and arctic animals, you are left with just 10 species: pronghorn, mountain goat, bighorn sheep, bison, elk, moose, mule deer, white-tailed deer, black bear, and grizzly bear.

If not for the end-Pleistocene extinctions just 13,000 years ago, there would still be another 40 species of North American megafauna. They would include five species of deer or moose, two llamas, a camel, three horses, four ground-sloths ranging from 400 pounds to 3 tons, a 600-pound armadillo, a 2,000-pound turtle-like glyptodont, two ox-like species, a 5-ton mastodon, a 6-ton woolly mammoth, and a 9-ton Columbian mammoth. Did I mention the 400-pound beaver? Before you jump into your time machine for a true North American safari, be advised that there were also scimitar-cats, American lions, and sabertooths, each as big as or bigger than an African lion. There were three huge bears, including the 1,800-pound giant short-faced bear, the largest mammalian predator that ever walked the Earth.

Now let’s return to the forlorn fruit of the Osage orange. Nothing today eats it. Once it drops from the tree, all of them on a given tree practically in unison, the only way it moves is to roll downhill or float in flood waters. Why would you evolve such an over-engineered, energetically expensive fruit if gravity and water are your only dispersers, and you like to grow on higher ground? You wouldn’t. Unless you expected it to be eaten by mammoths or ground-sloths.

According to my field guide, Osage-orange has a limited natural range in the Red River region of east-central Texas, southeastern Oklahoma, and adjacent Arkansas. Indians used to travel hundreds of miles for the wood, prized as the finest for making bows. Then European settlers planted it widely as living fences, taking advantage of the tree’s ability to spread via shoots from lateral roots. But Osage-orange persisted, and became widely naturalized long after the invention of barbed wire rendered them useless to farmers. The tree can now be found in 39 states and Ontario. If Osage-orange does so well elsewhere, why was it restricted to such a small area?

The Osage-orange tree once used this knobbly green ball to attract large mammals to disperse its seeds. (Credit: Mark Wells)

The answer likely lies in the disappearance of its primary disperser. Without mammoths, groundsloths, and other megafauna to transport its seeds uphill, the range of the species gradually shrank to the Red River region. In fact, fossils tell us that Osage-orange was much more widespread and diverse before the megafaunal extinctions. Back then, Osage-oranges could be found north up to Ontario, and there were seven, not just one, species in the Osage-orange genus, Maclura.

Another anachronistic tree is the Kentucky coffeetree, so named because early Kentucky settlers used its beans as a coffee substitute. Coffeetrees have tough, leathery pods with large, toxic seeds surrounded by a sweet pulp. Water cannot penetrate the thick seed coat to begin germination unless it is abraded or cut. Sounds like mammoth food to me. The natural range of coffeetrees is concentrated in the Midwest, but without its megafauna disperser, it is generally rare and mostly limited to floodplains.

Much the same can be said about the honeylocust, with its sweet seedpods up to 18 inches long. It is more common than coffeetrees, and is found in upland areas because cattle have filled in for the mastodons, camels, or some other dearly departed megamammal with a sweet tooth. The big-fruited pawpaws, persimmons, desert gourds, and wild squash may also have been dispersed more efficiently by recently extinct mammals.

Now when you see an Osage-orange, coffeetree, or honeylocust, you might sense the ghosts of megafauna munching on treats made just for them. (You may even see tropical ghosts in your local grocery store hungrily eyeing the avocados and papayas.) But you can also conjure megafaunal ghosts by considering the weapons designed by trees to discourage or slow their big mouths from eating the foliage.

Defenses like that of the seed pods from the honeylocust and osage-orange trees are all adapted to the strength and size of megafauna. (Credit: Mark Wells)

Osage-orange, mesquite, and hawthorn all bear stiff thorns, spaced too widely apart to do much good against narrow deer muzzles, but they would be unavoidably painful in the wide mouths of groundsloths and mastodons. Wild honeylocusts have vicious, trident-like thorns several inches long covering the lower trunk and branches. Hollies have prickly leaves. Devil’s walkingstick is festooned with wicked prickles. In all these heavily armored trees the thorns or prickles are present well above the reach of browsing deer, where they could still frustrate a mammoth’s trunk or a giant ground-sloth’s muzzle, but no higher. Cacti, Joshua trees, and other yuccas of the Southwest are particularly well armed in case the Shasta ground-sloths return.

If some trees have evolved big fruits so that huge mammals would disperse their seeds, why, now that those dispersers are gone, do they waste their efforts on big fruits that rot on the ground with seeds that will never germinate? If some trees have been in an evolutionary arms race with megafaunal browsers, why not disarm and save energy now that their enemies have been eliminated?

It’s true that such adaptations are now anachronistic; they have lost their relevance. But the trees have been slow to catch on; a natural consequence of the pace of evolution. For a tree that lives, say, 250 years, 13,000 years represents only 52 generations. In an evolutionary sense, the trees don’t yet realize that the megafauna are gone.

This would all be just another interesting natural history story if not for the very strong likelihood – many scientists would say fact – that humans, not climate change, caused the extinction of the megafauna, mainly by hunting. Humans first came to North America from Siberia just before the megafauna became extinct. That was also at the end of the last Ice Age, but all those species had been through over 20 previous ice-age cycles and come out just fine. The same two-step sequence occurred when humans first came to the West Indies about 6,000 years ago, Australia 50,000 years ago, Madagascar 2,000 years ago, and New Zealand less than 1000 years ago. Wherever humans first colonized the world, megafauna soon disappeared, an extinction pattern that is not correlated with climate change or anything else.

The thorns of the honeylocust once protected the tree’s foliage from the giant ground sloths and other megafauna. (Credit: Mark Wells)

Today, the evidence of human impact is all around us, but now we know that even the most pristine of wilderness areas have many missing pieces. We’ve learned to see the ghosts of the lost megafauna in the rotting fruit, poor dispersal, and useless thorns of Osage-orange, Kentucky coffeetree, honeylocust, and others. But what are we still missing?

Imagine the Columbian mammoth, larger than an African elephant and sporting curved tusks up to 16 feet long, eating 300 pounds of vegetation every day in your neck of the woods; assuming you live anywhere in the southern half of North America (if you’re in the north, just picture the smaller woolly mammoth). Now picture thousands of mammoth herds scattered across the continent. How did they affect trees and forests through their browsing, grazing, tromping, dispersing, and nutrient cycling?

Now add the mastodons, a bit more than half the size of Columbian mammoths, but still weighing 5 tons. Throw in the 3-ton giant ground-sloth and its three smaller but still big relatives. Remember the horses, camels, llamas, shrub-oxen, stag-moose, woodland muskox, and others. Don’t forget to think in terms of herds, and don’t think of them in the Ice Age. Rather, see their ghosts in the present, along your favorite forest hiking trail or peering over a fence along the interstate. How different would our forests and other habitats now be? What aspects of forest ecology do we not understand because of their absence? Is the coffeetree really a floodplain tree? Is an Osage-orange growing wild east of the Mississippi a naturalized alien, or a reintroduced native?

The first Americans could not have known they were causing extinctions, and they could not have understood the implications. But we no longer have such an excuse. As Aldo Leopold has advised, “The first rule of intelligent tinkering is to save all the pieces.” We have tinkered, lost some of the most important pieces, and tried to put many where they don’t belong. That we will continue to tinker there is no doubt. Everything will depend on how intelligently we do it. And that will depend, in part, on our ability to see the ghosts that haunt our trees.

Whit Bronaugh writes from Eugene, Oregon. Look for his work on Big Trees in the Spring issue.

This article was published in the Winter 2010 issue of American Forests magazine.

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85 Comments

I am so glad that you have this article and information out here on the world wide web. I am studying anthropology 1 (evolution, biological diversity, etc.) and this article fits right in with our discussion about the monoculture of any species, “the good the bad and the ugly”.

My own theory “borrowed from reading many non fiction books as a child” coupled with recent lectures on “gene flow” led me to conclude that the mega fauna and micro fauna did quite well in spreading the plant seeds around the earth. Of course climate variances also did their part in spreading the seeds, long before man “tinkered” with plant domestication.

Again thanks for your article. I am asking my professor if she would like to share with the whole class.
Yours,
Roberta L. Evans Newsome

I live in Indiana on a bluff overlooking the Wabash River. I have Osage orange, honey locust, and Kentucky Coffee Bean trees. Although the article states that only mega fauna eat the hedge apples, I don’t believe that’s true. Here’s a picture of some hedge apples on the ground in October. After the snow covered the ground there were all kinds of very small animal prints in the snow around the hedge apples tearing into & eating the seeds. There were never any deer tracks, only rabbits, squirrels, and the tiny prints which I think might be mice or possibly chipmunks. Wish I had taken a picture of the “torn apart” hedge apples with all the tiny animal prints! Now that the snow has melted, the hedge apples are completely gone.

Good observation. Those small small mammals are typically referred to as “seed thieves” insofar as they consume, but do not disperse the seeds. Megafauna would have eaten the fruits, allowing the seeds to be dispersed, undigested. The little critters chew and consume the seeds, destroying the reproductive germ.

True that smaller mammals will eat the fruits, and probably always did, but the masticate the seeds a little too thoroughly and therefore don’t aid in seed dispersal like a larger mammal would. The seeds would just go through undefeated.

I have been collecting seed of Kentucky coffeetree from all round its native range, making 10 collections in Indiana from native wild areas to plant out for a comprehensive collection of this species. I would be interested in the location of your trees on the Wabash to see how this compares to my other collecting sites for possible future collecting.

Nice piece. There is a row of Osage oranges behind the Maryland warehouse in which I work. Small armies of squirrels wait until the trucks have crushed the fruits against the pavement and then gorge on the mash.

I grew up on a farm in Northern Illinois. My grandfather told me that The Osage Indians grew the trees to use the flexible and strong limbs to make bows for arrows. Anyone ever hear that and that if you have spiders you can trough a few under some furniture in your house or garage and spiders supposedly will stay away. Also, farmers found them useful for fence posts. Fresh cut trees rooted and grew along the fence line.

However, the question should be asked: Why do these plants have thorny branches? Acacia trees have thorns for one reason—defense against browsing animals. Osage orange did not develop thorns under the evolutionary pressure of squirrels and deer.

This is a wonderful article. Thank you very much for sharing it! I do have a small quibble, thought. This time of year, I routinely see Fox Squirrels eating osage-orange fruits. And I’ve seen it every year since I started paying attention, in the late ’90s. And Fox Squirrels, I believe, live in the relict range of osage-orange. So I don’t think it’s quite true to say that no native mammals eat them.

Bill Stringer….I have tried eating Maclura pomifera (Osage Orange or Hedge Apples)(The common names were so enticing.. but certainly were not based on similiar. And they are related to mulberries and figs. out to be good.. Wrong…….Never found a stage when it was edible..The things are so full of latex when they first fall that you can barely shove a knife through them.Much less chew them..Then they go to rotten.. Never found them sweet.. I doubt country boys eating them and spitting out the seeds ever contributed to their dispersal.

Honey Locust, Paw-paw, and Persimmon are also food for humans and were purposefully used as such (and propagated by) the humans that were descended from those that hunted out the mega-fauna. If these species are declining, it may be due to another extinction event and the elimination of human reliance on these species and hence their interest in cultivating them.

As for the invasive Osage Orange, if you would like some, please come by my place in South Carolina and dig up all you want. They are not killed by Dicamba, Triclorpyr or fire and I’d like for them to go away!

Chris I thought the same thing about experimenting with elephants as stand-ins for the mammoths & mastodons. Especially for the Kentucky coffeetree. The more I learn about that species the more intrigued I am by it. Supposedly elephants can handle certain toxic plants so I’ve wondered if they handle coffeetree?

As as been stated, squirrels and deer routinely eat osage orange. I do not understand the reference to Pawpaws. They are very widespread and quite common, covering large areas along streams in my area. If you want to gather Pawpaws, you need to get there before the local animals get them.

Cattle and horses eat osage oranges. If one would walk a pasture in Texas, no fruit will be found under female trees. One rancher told me that he has to dump the fruit into the adjacent fenced field to keep the horses from knocking down his fence. Many small animals will eat the seeds in dried or rotten fruit. The seeds are high in protein, oil and carbohdrates. Deer do eat the fruit and spread the seed. Especially in Texas, the return of the native osage orange to the Post Oak Shavannas and Cross Timbers will bring back the natural wildlife habitat lost
during the last 150 years.

Beautiful but also a fluff piece by the topic’s own admission. Animals change their ecosystem and so did we. What we are doing is not counter to the natural order, it’s part of it. No human behavior is now, or has ever thus far been unatural. Those that we’ve pushed out themselves pushed out competing species before them, and they before them, ad nauseum, throughout the who of evolutionary history.

Pity this article took such a sappy turn for the altruistic. It was almost a valuable read.

To say that “nothing man has ever done or is doing is unnatural” is pure semantics & a self-deluding desire for blamelessness. Yes, other species & natural events have caused plenty of extinctions in the past. &, Yes, some of those extinctions have occurred almost instantaneously, at least in evolutionary terms, but none of those mass extinctions until now (“now” also including 13,000 yrs ago) were caused by a single species, only by rapidly changing environmental conditions.

Any species’ ability to adapt is time-dependent, or more exactly, generationally dependent. Thus fruit flies, for example, can adapt far more quickly than, say, woolly mammoths. It’s unlikely that man was even aware that he was killing off mastodons & woolly mammoths, given their almost certainly long gestation period & small # of offspring. Now that our current technology has moved beyond stone weapons & includes substantial & even faster changes to land, water, & air, many other species lack the capacity to adapt to the changing conditions we alone are causing. As you point out, there are & have always been other changes occurring, but these typically occur at a rate that allows the majority of species to adapt to them.

What man has been doing in these last few millennia that is unprecedented is producing sweeping environmental changes AT A RATE that’s never been seen before (at least as caused by a sole species rather than by a meteorological or climatic event.

So if it helps you feel better to say that we’re just acting like all other species by doing things to our own advantage at the expense of other species, you may want to consider how poorly we understand what impact the current human-caused mass extinction & climatic changes (global warming, acidification of oceans, etc.) is likely to have upon our own survival.

Do you folks there in Australia cultivate pawpaws for the fruit? Its growing slowly as a cultivated fruit here in the Midwest. Its kind of like a banana (in flavor). It would be interesting to see how well Kentucky coffeetree does there as an ornamental. Its starting to be used more and more here as it basically has no disease or insect pests and can handle periodic drought & urban conditions. It wouldn’t be an invasive threat there because the seeds are so hard to get to germinate & it would have to grow in the cooler & more temperate parts of your country. Food for thought!

In Oklahoma these are horse apples for those that eat them. From previous research, Osage Orange grew only in north Texas and the Caddo made “slats” of the hardwood and traded with other tribes. When Coronado brought horses and long horn cattle to the new World, they began “broadcasting the end product.” Here in Alabama we have a huge Osage Orange tree. thanks Coronado.

I really like the article but the author theorizes that humans are responsible for the extinction of megafauna then why are the largest of today’s megafauna found in the birthplace of the human species, Africa?

Your question, “[if] humans are responsible for the extinction of megafauna then why are the largest of today’s megafauna found in the birthplace of the human species, Africa?”, has, well before this, occurred to scholars who study megafauna extinctions.

It was in Africa that humans evolved from gatherers of plant foods, predators of small animals, and scavengers, to highly effective hunters of large game. This process took millions of years. In the immense time period that encompassed that long, gradual change, the African megafauna had the time it needed to evolve defenses to human predation — including the ability simply to recognize that such small creatures were a threat, and needed to be avoided before they could get within spear, and then bow-and-arrow, range.

This hypothesis is corroborated by the fact that the region of the globe that has the second-highest number of megafauna species that have survived to modern times (most notably, elephants and rhinos) is South and Southeast Asia, which is also the region outside Africa that has had hominid inhabitants the longest. Homo erectus, a predecessor of Homo sapiens, and probably the first hominid species to control fire and develop hunting tools that could kill large animals, dispersed from Africa into the warmer parts of Asia perhaps 1.5 to 2 million years ago. As in Africa, this long period of co-existence with humans that were developing hunting technologies gave Asian megafauna time to adapt to humans as predators.

In this respect, those regions of Africa and Asia contrast sharply with Australia, Europe, North Asia, the Americas, Madagascar, and New Zealand, where migrating humans that already possessed advanced hunting technologies appeared suddenly, in terms of the evolutionary time scale, and found megafauna that did not recognize them as threats, species that were unable to adapt to the new threat, before human hunting, perhaps in concert with other factors, depressed their populations to catastrophically low levels.

I read a fascinating article on this subject. Its thrust was that the fauna we had the least impact on was that of our origin (i.e. Africa) because other species present had the longest time to adapt to humans before we became such skilled competitors.

As we evolved, they evolved some defenses against us. Once we began spreading, however, we encountered new species that had not had the same inoculation period against us.

I don’t necessarily advocate this, but it does seem as though the areas we humans colonized the most recently are the ones we did the most damage to. In other words, we had the least impact on African animals, more on Eurasian species, still more on North & South American and perhaps the most on Australia and Oceania.

I responded to a previous reader with a similar thought about using elephants. If they handle the fruits of Osage Orange & Kentucky coffeetree and the seeds survive their digestive processes then I’d say this really gives credence to this megafauna hypothesis.

What a brilliant article. I am so glad a Facebook friend shared it and I was able to read it. I have now stored it on a memory stick so I can refer to it in the future (with an acknowledgement to you, of course!)

If we replicate the Ecologic Services of the extinct megafauna, since 7 billion of us makes us the new Megafauna, then we could build back Soil Carbon with massive increases of Net Primary Production. An ecology not seen for 12,900 years.
An Ecology not limited by Phosphorous, Sodium & lost Soil-C.
A great synergy of the work restoring mine scarred lands & developing consumer, Horticultural & Agricultural markets.

Biochar systems have so many market applications yet to be cultivated; “Carbon Fodder” feeds for Livestock, Plant Chemical Communications, (plant signaling), even Char building materials such as Biochar-Plasters which block Cellphone signals, the potential markets are massive.

CoolPlanet’s investors & CEOs project (assert) that they will be the first Trillion Dollar Company, based on their $1.50/Gal. cost to produce Bio-Gasoline.

For a complete review of the current science & industry applications of Biochar please see my 2014 Soil Science Society of America Biochar presentation. How thermal conversion technologies can integrate and optimize the recycling of valuable nutrients while providing energy and building soil carbon, I believe it brings together both sides of climate beliefs.
A reconciling of both Gods’ and mans’ controlling hands.

Greetings,
There are animals that will eat them, deer, squerill (sp).
The wood is used for making bows ( archery) fence posts and many other items.
The fruit can be cooked as the latex dissappearsin from the heat. It tastes like cauliflower.
Medicinal uses also.

somebody help me! i can’t find the source where i learned:
1. maclura pominifera is the most planted deciduous tree in n.america, vis, hedging during mid west settlement.
2. was on the chicago market, seed and nursery, ’till the ’20s.
3. is mentioned in the congressional record during Jefferson’s administration, reflecting hired Brittish exploration of Louisiana purchase, noting potential for hedges.
4. highest BTU of any north american hardwood.
5. rot resistance 2nd to cyprus
i planted several thousand in hedges nearly 10 years ago and still haven’t seen fruit. sheep, llamas, goats, cattle, all nibble the leaves.

Thank you for this most wonderfully informative article.I have wondered for years what type of tree yielded this bizarre looking fruit,which I have for years spotted at a single location in New York City’s Central Park, located at the entrance of 100 Street and Central Park West.The grapefruit sized seeds are scattered along the steep staircase towards the pond right now.

A beautiful article. I hope that people will soon realize what we have sadly lost and try that much harder to protect what remains. If we continue to take it for granted and let the hard hearted and greedy among us destroy it all, one day we, or our children will wake to find the world so much the poorer and sadder. Irretrievably so.

I love the idea of exploring the prehistoric/pre-human world, especially the mid-Miocene (but I’d take Pleistocene or prehistoric Holocene too, though the former would be a bit cold, and the latter uncomfortably close to the overkill campaign). I hope if one day a time machine is invented someone will resurrect me and send me back.

Humans were responsible for a very little percent of the extinction of megafauna. There was a period of 100s of millions of years where Earth didn’t contain the super rare evolved form of algae that is required to break down trees back into soil, so when for millions and millions of years, when trees would die or be knocked over, they literally would just sit there forever or until lightning would start a fire, and then some of the largest fires Earth has ever seen. Eventually what happened is that the ratio of oxygen in our atmosphere started to rise (I think I remember it went up by 5-7%, which make not seem huge, but actually is, which is a big part of the reason why eventually dinosaurs could even exist at all. Without the extra oxygen and different atmospheric conditions, it wouldn’t have gone down the same evolutionary paths.

Eventually that bizarre algae (that we now take for granted as a simple fact of life) was randomly evolved/mutated, and then quickly took over the planet, and changed Earth’s entire tree ecosystems, which many argue was FAR more impacting to the planet than crappy human behavior has been so far, because again, the algae has remained for millions of years (I think it was around 325 million years ago is when we think it was created). Dinosaurs started to be less effective at survival compared to megafauna, because small creature populations exploded, and at first this was a boon to the large mammals, but then animals got smaller and smaller in larger and larger populations, and then the megafauna had to deal with smaller meals and working twice as hard or twice as long to keep eating the same amounts, and all the while, the oxygen ratio in the atmosphere continued to slowly drop, so eventually today’s sizes of predators and prey and plants all became the new normal, and then mix in the Ice Ages, and you have even more extinctions as animals hit their breaking points. For the author to call Ice Ages no big deal to wildlife since several of them happened, is absurd and laughable.

As wildlife slowly changed to smaller sizes, and Ice Ages knocked a few more species out for good, eventually humans came into the picture in large numbers and we also pushed a few species past their breaking points, but the evidence is strong that they would have perished (over a longer timeline) anyways if our atmosphere would have stayed the same as it was 13,000 years ago. Some predator mammal species would have continued to survive. Some would not.

I think the video documentary about this algae is After Life: The Strange Science of Decay, but I could be mistaken.

50 million years where trees never decayed! It was a 50 million year puzzle, but fungi eventually cracked the code and did more total harm to wildlife species than perhaps any other form of life in Earth’s history!

You have given a textbook example of taking disparate facts, failing to grasp how they are related — or, to comprehend that they are •not• related — and pushing them together to create an argument that is simply incoherent. You have missed the point of Bronaugh’s argument, by conflating wildly disparate time scales, and by simply being oblivious to the radically different contexts of facts that you attempt to link together, but are, in reality, only superficially similar — such as atmospheric changes and megafauna extinctions hundreds of millions of years ago, and atmospheric changes and megafauna extinctions a few thousand years ago.

That is to say, you’re comparing apples and oranges (or, one might put it, hedge apples and Osage oranges . . . except, those •are• the same thing).

To add to my previous comment, here’s a quote from one of the top Reddit comments in that thread:

“This period of elevated oxygen levels (30-35%, versus the 21% of today) lasted from the Carboniferous through the end of the Cretaceous, 65M years ago. It is extremely likely that the large-type dinosaurs simply cannot exist in our current atmosphere. They probably needed these increased oxygen levels to reach the energy production density that these massive creatures are estimated to require.”

So it was 9-14% estimated raise in oxygen, not the 5-7% I was guessing. Also, it was around 400 million years ago, not the roughly 325 mya I was thinking.

I have 120 acres. The osage-orange is a problem – sprouts and trees all over. Continuously have to spray and kill them. To say nothing eats and spreads the seeds is BS. Thus the whole premise of the article is wrong.

I find it surprising that the theory that human hunters caused the massive extinctions of mammals about 11,000 years ago in this article. I thought this theory had been soundly discredited by archaeologist, especially Donald Grayson and David Meltzler (see “Requiem for North American Overkill” (2003) in the Journal of Archaeological Research 63:185-213, and First People in a New World (2009), University of California Press, p. 262-265). However, it’s hard to discredit a simple and compelling theory. especially one which appeals to those predisposed to blame humans for all that might be wrong with the world today.

The hypothesis of anthropogenic megafauna extinctions has been challenged — but hardly discredited. As Bronaugh notes, since the commencement of the Quaternary ice age about two and a half million years ago, there have been many episodes of both global warming and cooling. Each of those has been challenging for some portion of the global megafauna that existed at the time. But through each transitional period, most of the megafauna species around the globe managed to survive.

Within the past 50 to 70 thousand years, however, periods of climate change coincided with extensive, widespread extinctions of megafauna, extinctions that were, in scope, unprecedented in the Quaternary. The climate change itself was •not• unprecedented. Why, then, would it have had an effect on megafauna survival that it never had before? It is very striking that these recent megafauna extinctions on large land masses appear to have taken place shortly after the initial migration of modern humans to places that hadn’t previously known humans.

It is certainly true that correlation does not •necessarily• establish causation. But I have yet to see a satisfactory explanation of why the most recent set of climate changes should have had — for reasons •apart• from concomitant migrations of modern humans into new territories — such devastating effects on megafauna populations, when previous episodes of drastic climate change had not had similar effects.

And conversely, why did megafauna populations in Africa and South/Southeast Asia, which •had• learned to co-exist with modern humans as those humans evolved, •not• suffer similar widespread extinctions, when those regions were experiencing climate change at the same time that change was supposedly killing off many megafauna species in other parts of the globe?

Again, these are questions that those who wish to deny the significance of human predation, or human alteration of habitat, to megafauna extinctions in the past 50 thousand years or so, have yet to come close to offering persuasive answers to.

here about 30 years ago the (then) boys found a mamouths tooth. Last year I picked up what I thought was a piece of wood; it was wood but fossilized. I went back and discovered where it came from: near the base of a cliff with about 80 feet of glacial till above, from the last ice age at Juan de Fuca Straits near Sequim Bay.

Very informative article. The reference to the Ky Coffee Tree’s sweet flesh covered seeds brought up several questions. The pods look very similar to those of the tamarind tree from the tropics which are eaten by humans, me included. Did the Native Americans use the Coffee tree as a source for a sweet food in the same manner as the tamarind? The first settlers must have gotten the idea from someone, if no one dared try it first.

I hate to punch a hole in your nice theory, but many times I have sat in the woods while stalking whitetail deer in middle Tennessee and watched Gray Squirrels munch out in Osage Oranges all the while scattering the seeds and fruit everywhere. I have also seen evidence that the deer eat them as well as the Honey Locust pods when they are low enough to the ground.

I commend Mr. Bronaugh for writing this article. These trees don’t get the full appreciation that is due to them. During the last few weeks I’ve been researching the Kentucky Coffeetree and I’ve found there really isn’t much out there on it. Most of the information tends to be repetitive. I grew up in southeastern KS which is in this species native range and though they are around they’re never really common. Up in Kansas City I’m starting to see some being planted since the advent of the emerald ash borer’s appearance. Since coffeetree at this point in time has no serious insect or disease threats its starting be be used as a replacement for ash trees. What is sad is that so many times its clones of the male trees such as “expresso” that is being used and this isn’t helping the tree’s genetic diversity. It yields lovely wood that can be used in cabinetry, bowls, etc but it can be hard to come by. This is a species that needs to used more in a variety of ways!